The best thing you can do is post images/gifs of what you're working on social media (twitter, tumblr, reddit) and see how many likes/upvotes it gets. As you post things you will be able to compare either to your past posts or to posts of others on how well it does, and if something goes significantly above/below average you can derive that it likely looks better/worse than whatever it's being compared against.

In my case it's about CSS and WEB UI/UX, so it's a bit hard to do what you say but the problem is still the same.